Technically, a not-for-profit taxable subsidiary. (That makes a difference because the company purpose of Mozilla Corporation is still not to make money/raise shareholder value, despite the fact this it is fully taxable like any other company).

Isn't the purpose of Mozilla Corporation exactly to make money which inures to the benefit of its sole shareholder (Mozilla Foundation), making it just like any for-profit company except that it happens to be owned by a nonprofit?